June 2021
Volume : 01 • ISSUE : 03
Examining the benefits of screen printing in the modern market change, various existing technologies remain very much at the forefront of PSPs’ minds. One such technique is screen printing, which, although perhaps more expensive than digital methods, produces high quality output to those who choose to run with it. But is this enough to ensure its long-term future in the fast-paced market that we find ourselves in? FESPA.com speaks to some of those in this sector and finds out how screen printing continues to serve them well. Vibrant colours and special effects
D
espite the influx of digital machinery in recent years, screen printing remains the choice of technology for some print houses. Rob Fletcher investigates how and why this type of kit is standing strong. There is no understating the
impact that digital technology has had on the print industry. The mass influx of digital machinery had reshaped the industry to the point where many print service providers (PSPs) cite digital as their preferred technology. However, despite such widespread
MagnaColours specialises in water-based screen-printing inks, focusing on the global textile industry. The company supplies the market with environmentally-friendly, water-based inks, as a high-performance alternative to PVC-based inks. Helen Parry, managing director at MagnaColours, says there is still a place for screen printing, explaining that while digital is good for shorter
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runs where some elements of personalisation is desired, screen print serves as a better option for high volume runs. “Screen printing applies a thicker print to the fabric so vibrant colours are possible even on dark shirts and speciality effects like glitters, puff and high density, none of which are achievable using digital printing,” Parry said. “It is cost effective for long runs and offers users the opportunity to create vibrant colours and special effects. “It is a highly versatile print method, capable of printing onto a wide range of fabrics, light or dark, with excellent wash durability that can withstand high performance wash temperatures.” In terms of how MagnaColours can support this market, the company recently release a line of pigment dispensers. Marketed as MagnaTint, these dispensers connect to the firm’s MagnaMix colour mixing software and instantly dispense pigments for a given pantone reference or shade. MagnaColours has also developed a new under base ink to provide plastisol printers with an economical solution to improve the handle and softness of their prints, whilst also achieving considerable cost savings for printers. “Magnaprint Killer Base is designed to be used as a water-based replacement for the first layer of plastisol ink or as an alternative option for printers using discharge under bases,” Parry said. Building on this, Parry says these ‘greener’ inks will increase in popularity as the industry leans more towards environmentally friendly production.
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Dominating new and existing markets Elsewhere and inks giant Sun Chemical is also championing screen printing as a reliable technology. Robin McMillan, product manager of industrial and graphics Europe at the company, says it continues to be the favoured print process for various applications and markets, as its ability to print on numerous substrates with multiple ink types makes it stand out from other print processes. McMillan said: “Many commentators have been predicting the demise of screen print for over 20 years now. Clearly its popularity has been heavily affected in previously traditional markets such as graphics, POS and textile, where digital print is now leading the way. “However, while pressure from other traditional print technologies, such as litho and flexo, have also had an impact on screen print, screen continues to dominate in many existing and new markets.” McMillan said Sun Chemical continues to support both the graphic and industrial markets with new ink developments. For the graphic market, this has seen a shift towards products that can be used for a wide range of applications – making inks that are truly universal for modern PSPs, which minimises the number of inks they need to produce jobs on different substrates for different applications. In terms of industrial print, McMillan said developments tend to be very market-specific, with inks developed to suit either an existing market or application, or those emerging through product
developments, either for decoration or as a functional part of the end product. McMillan added: “The rise of digital and especially inkjet is bound to have an ongoing effect on screen print and in fact all current print technologies, but the timescale for this and the actual penetration is yet to be seen. In the meantime, therefore, screen print will continue as a very viable process, favoured by many markets for a few years yet.” Building for the future Also in this market is Proell KG, a German manufacturer of screen and pad printing inks, as well as specialised ink systems and adhesion. The company is also a supporter of in-mold decoration and film insert moulding (IMD/FIM), a technology used to help produce automotive applications such as radio and climate control panels, as well as covers and displays for smartphones and laptops. During the IMD/FIM process, finished decorated components are produced by inserting decorated, formed and trimmed semi-finished film products into the mold during the injection molding process. For this technology, various PC and PBT blend films and hard-coated films, as well as a range of PC resins, are used for injection moulding. With film insert molding means, a second surface screen printed film is formed, trimmed and then inserted into the cavity of the tool and back moulded onto the ink directly. Stefan Zäh, manager marketing communications at Proell, says that the use of screen print in this process proves that the technology has an exciting future in the print industry and the many markets it serves.
Zäh said: “Screen printing is the most versatile print process as fine details, large areas, transparent and opaque colours, lacquers and special pigments can all be applied easily. “The outstanding brilliance and durability of screen printed colours, compared to other printing techniques, are of greatest interest for the decoration of design oriented IMD/FIM parts. “Night design applications, which are particularly important for climate control panels, keypads, and switches can be realised in screen printing technology by processing transparent, semi-transparent and highly opaque colour shades.” Shifting up a gear while it is pretty clear screen printing has a future, there appears to be a call for the technology to evolve in order to keep up with other developments within the market. SignTronic and Grünig are both very much of this mindset, working hand-in-hand to promote THE LAB concept, based on computer-to-screen (CtS) direct exposing technology and screen automation. Andreas Ferndriger, CEO and owner of SignTronic, as well as marketing director of Grünig, is under no illusions that screen printing offers solutions where other printing methods come to their limits, but is seeking to evolve this technology, hence the focus on CtS. Ferndriger said: “Screen print means no colour limitations, deposit limitations, substrate limitations or size limitations. Further to this, if the main focus is set on simplifying screen making (CtS technology and automation) then the additional benefits will be more output, higher
quality and lower costs per screen. “New technologies such as CtS direct exposing with UV-LED-DUO Generation, automatic stretching and gluing systems modular or in-line coating machines, fully in-line screen cleaning systems, as well as wear-free frame cleaning machines that only use water, are available and possible to adjust to individual customer needs.” Ferndriger accepts more awareness of badly managed pre-press departments is required in order for the screen printing market to make progress here. He said that processes in pre-press must to be both reduced and automated, while new technologies should be implemented to support this development.
He added: “With more output, higher quality and lower costs per screen the future in screen printing is bright and almost without limits.” Ferndriger’s comments conclude this debate in a rather orderly fashion; there is no doubt that screen print offers a number of major benefits to users, but there is seemingly room for improvement. There are plenty of encouraging signs that the manufacturers in this market are seeking to push the technology further so that it not only makes life easier for the user, but also helps them create higher quality output.
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Create magic with Haptic Print effects
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aptic technology is a way of communication which can create a unique experience by touching or feeling the surface. These are primarily used in automotive (interiors, panels) and electronic (laptops, mobile covers) industry to differentiate their product from regular plastic feel. These industries now want the same effect on their packaging and promotional material as well. Many printing effects like silky, soft, velvet, rubber, anti-skid or anti slip fall
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into this category. These inks can be printed on variety of substrates like metals, paper, plastic and foils to bring a luxurious feel which in turn can be perceived as “one of a kind product” in the market. These stunning visual impressions can be used as a tool to enhance the print experience of print buyer and consumer. Printers can offer these products to make superior quality cartons, brochures, pamphlets and promotional material.
What is exactly This Haptic Feeling? For a long time humans have relied on touch to convey feelings to themselves and others. Any coarse feeling surface sends a negative effect to brain then a smooth one. Even great civilizations like Egyptians and Mayans lay emphasis on designs which were soothing to eyes and touch. When one touches this type of surface, the mind conceives the touch and sends signal to parietal lobe
and sends signal to parietal lobe which in turn interprets the signal as a calming effect. Researchers have for a long time tried to quantify sensory perceptions into numbers. Appeal of these effects on our senses is great, but care should be taken while printing, especially taking into account wear and tear of the paper and mechanical properties of the inks. One needs to understand these coatings and incorporate the effects in designs in such a way that it will enhance the beauty of the final product. Various uses of these functional coatings should be discussed with buyer before commencing the job. For example a job with silky feel coating might give problem during cutting process and have to be punched. Haptic coatings can be applied to substrates like metal, plastic, paper via spray, dipping, flexo or screen printing depending on the application. These coatings are widely available in solvent and water base system (2 component) and are mostly employed for coating purpose. In past 5 years 1 component water base system for
application on paper was introduced and was received very well. For screen printing purpose formulators have very few options to develop inks for water base system. Here UV inks has come to rescue and shown great potential as it has a better pot and shelf life, is easier to formulate and mainly due to advancement in the chemistry of oligomer and additives. UV haptic inks retains the many features of velvet or soft feel effect like matiness (contrast effect), warmth
and rich feel, surface drag, colour depth while maintaining the aesthetic features. While screen printing cannot compete with lamination or coating, it does have its advantages especially while printing small quantities or covering a particular spot on the print. "CoLoRs Printing Ink has recently developed these screen UV inks, for more details contact on info@ colorsuv.com"
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LED Intensity Measurement and Challenges
T
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he same challenges that exist for measuring visible LEDs also exist for measuring UVLEDs. The light emission from an LED is vastly different than a point source. This poses challenges in quantifying its intensity. Limitations in standardizing the measuring techniques of LEDs include:
built into the LED packaging. • LEDs do not follow the inverse square law (i.e., intensity of light reduces by square of the distance) similar to extended sources. That means that even for the same solid angle, intensity measurements could vary with distance and could be unpredictable.
• A point source, by definition, has a constant radiant flux in all directions but LEDs do not follow equal radiant flux rule. This is because most of the LEDs have micro-optics
There has been an incredible amount of research done in recent years at various public and private organizations for developing measurement techniques.
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Due to several variances affecting intensity measurement of an LED, the Commission on Illumination (CIE) established a standard method guide for LED measurement document. One of the most popular ways of measuring radiant flux for an LED is using a photometer at a specified distance and specified area recommended by the CIE. Individual LEDs may be characterized this way under controlled laboratory
conditions, but the recommended procedure cannot be easily applied to LED clusters and arrays (the arrangement of UV-LEDs used for UV production curing applications). In order to measure total radiant flux, an integrating sphere is used. The document describes the placement of an LED in a calibrated integrating sphere and measuring total radiant flux. When performing a measurement using an integrating sphere, the intention is to capture all energy. In real-world applications, the user might be more interested in capturing the LED radiant flux for a small solid angle that is also sometimes referred to as “useful radiant flux.” In order to make this measurement, the CIE updated their guidelines in the recently published CIE 127:2007 document to include the term “partial” radiant flux. Traditionally, intensity measurements of a point source are done using luminous intensity. As described earlier, most LEDs are not point source and do not follow the inverse square law. LED intensity measurements claimed by a manufacturer could vary when the end-user performs a similar measurement. When performing a measurement, it is always important to know conditions and uncertainties associated with the measurement. Sources of uncertainties that can contribute to the uncertainty of the
measurement include: • Radiometer calibration uncertainties • LED short-term wavelength drift • LED temperature drift • DC regulation for LED • Optical alignment Industrial applications and setups make it more challenging to easily control and measure the above parameters. As stated, LEDs have a narrow band emission and, hence, could have short-term or long-term wavelength drifts due to temperature variations or degradation over a period of time. Most integrating type radiometers were originally designed for UV-arc and microwave sources, and have a bellshaped response curve across the UV band of interest. 365 nm LED
Using a radiometer designed for arc and microwave sources can lead to large errors in measurement if UV-LED output happens to fall on the rising or falling edge of the optical stack response. If the LED is binned very close to 365 nm, the EIT UV-A response does a good job of measuring this source. But even a small drift in the LED spectral output or variations in how the LED dies are binned can generate different responses in the radiometer, which can have a pronounced impact on the measurement. 395 nm LED Measuring the output of a 395 nm LED with a radiometer utilizing an EIT UV-A or EIT UV-V response can lead to wide variations in the reported irradiance values. The output of a 395 nm source is grouped “around the 395 nm line” with variations based on how
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So, while it is possible to get a reading with a UV-A or UV-V bandwidth radiometer, the sharp cutoff at this wavelength means that the readings may reflect only 5-50% of the actual 395 nm LED. The large variation can result from the output being on the steep slope of the response curve, variations between measuring instruments and variations between the LEDs themselves. Because of these variables and their combinations, it is hard to apply a correction “factor” to the UV-A reading or UV-V readings to any single instrument.
individual LED dies are binned; how the array is assembled; and the stability of the product over time. These slight variations are normal. It is also normal to expect slight variations in each radiometer due to slight variations in the optical components (filters, detectors, etc.) and electronics.
The output from a 395 nm LED clearly falls between the EIT UV-LEDs used in UV coating. UV-A and EIT UV-V response curves. The steepest part of the shoulder of each optical response curve is in the output range of the 395 nm LED.
A better approach to measuring LEDs in the 395 nm range is to use an instrument with a response curve that better matches the source. EIT has developed a subset of our 320-390 nm UV-A bandwidth now designated as UV-A2. The UV-A2 response curve is especially sensitive in the 380-410 nm regions. This region better covers the 395 nm LED since under normal conditions the source does not fall on the steep shoulder of the response curve. Extensive testing was done to get the UV-A2 radiometer optical response to proximate a “flat top” response. A “flat top” response limits the shifts in the measured values due to slight spectral variations in the source. The UV-A2 response bandwidth inherits a Lambertian spatial response by design from early generation radiometers that further reduces measurement.
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